For a long time plant biologists knew that a number of species of rhizobacteria (bacteria naturally occurring in the plant rhizosphere) beneficially affected plant growth albeit by employing different mechanisms. These mechanisms include: 1) contribution to the nitrogen economy of the plant by fixing atmospheric nitrogen (N2); 2) producing growth stimulant compounds such as various auxins; and 3) inhibiting a number of plant pathogenic bacteria and fungi. Therefore, it was believed that naturally occurring rhizobacteria contributed not only to increased plant growth but was also to protect plants against pathogens.
Numerous types of rhizobacteria have been isolated and applied exogenously to plants as growth enhancers with a stated goal of minimizing the need for environmentally harmful chemical pesticides and fertilizers. However, due to the complexity of the rhizosphere, bacterial additions to the soil do not result in the types of increases in plant growth or productivity expected by the plant growers.
Thus it would greatly benefit our environment to have naturally derived microbial products for increasing plant growth and for reducing the need for applications of pesticides.